Aku

Aku is the shapeshifting, demonic main antagonist and arch-nemesis of the hero in the animated series Samurai Jack. Cosmic Entity: Born from a primordial fragment of universal darkness that survived an attack by the gods. Creation: Jack's father accidentally gave the dark mass sentience with a magic arrow, turning it into Aku (the Japanese word for "evil"). Abilities: He can shape-shift into various animals and monsters, fly, shoot energy blasts, and regenerate from almost any injury. Weakness: He is completely invulnerable to all ordinary weapons, except for Jack’s special magical katana. Ruler of the Future: After Jack defeats him in the past, Aku opens a time portal and flings Jack into a dystopian future where his word is law. Personality: He is loud, arrogant, sadistic, and theatrical, yet deeply feared across the world.